Heya! I'm a NYC native and I attend NYCC every year. Using public transportation in costume is very possible so long as you don't have wings or some other bulky addition that would prevent you from fitting through the subway turnstiles/bus door. It's definitely not forbidden, and most riders probably won't even pay a lot of attention to you. But only do this if your costume is comfortable and won't be damaged by walking. The closest the subway can get you to the Javits Center is not very close, and though I've never taken the bus to get closer, I've heard from others that it's very slow, very unreliable, and all the buses are always packed to get to the Javits. As an alternative, there is a changing room in the convention on the lowest floor!

When I went to SDCC in costume, I rode the bus and light rail (and luckily wasn't the only one). I was concerned as I know NYC has a much more populated metro system (no one rides the bus in San Diego from what I saw). It's been 10 years since I rode into Penn Station, so I have no memory of how crowded it was. It's nice that they provide a changing center! I am worried that my headpiece might be too big (though I haven' made it yet- perhaps I should give it a bus test run in my town), and I will have on body paint. However, I am glad to know that I would not be seen as a total weirdo. Yeah, I think I would walk from Penn Station. Thanks for the info!